Implantable cardiac stimulation devices are well known in the art. Such devices may include, for example, pacemakers or defibrillators. These devices are generally implanted in an upper portion of the chest beneath the skin of a patient within what is known as a subcutaneous pocket.
Traditionally, therapy delivery has been limited to the right side of the heart. To that end, one or more stimulation leads are implanted within the heart. The leads may include one or more electrodes positioned within the right ventricle or right atrium, or both, of the heart for making electrical contact with their respective heart chambers. Conductors within the leads couple the electrodes to the device to enable the device to deliver the desired cardiac stimulation therapy.
Recently, cardiac stimulation leads and methods have been proposed and even practiced for delivering cardiac stimulation therapy from or to the left side of the heart. These lead structures and methods involve lead implantation within the coronary sinus and/or the great vein of the heart and/or coronary sinus veins, for example, since the coronary sinus is closely adjacent the left atrium and extends into the great vein which is adjacent the left ventricle of the heart. Electrodes thus placed in the coronary sinus and great vein may be used for various forms of cardiac stimulation therapy such as left atrial pacing, left ventricular pacing, and even cardioversion and defibrillation, for example.
Cardiac stimulation lead placement within the left side of the heart can require lead placement in difficult-to-reach veins and arteries. Two methods generally practiced for lead placement are stylet placement and guide wire placement. Stylet placement is a common practice for lead placement in the right side of the heart. Guide wire placement is less commonly employed.
Currently, there is debate in the art as to which lead placement method is best for lead placement in the left side of the heart. Each has its advantages and disadvantages. Stylet placement has the advantage of simplicity and involves minimal components, sometimes an important factor during a surgical procedure. In some patients with small veins or unusual cardiac vein anatomy, the guide wire placement method may have an advantage in facilitating lead placement. It is likely that both methods will find future use.
Cardiac stimulation leads are designed for only a specific lead placement methodology. More specifically, such leads are configured for either stylet placement or guide wire placement, but usually not both. Unfortunately, this may result in a physician finding, during an implant procedure, that a lead already attempted to be implanted must be discarded in favor of a lead designed for a different implanting method. This not only represents additional cost, but it also can complicate the surgical procedure.
The present invention provides an elegant solution to the aforementioned problem. In one embodiment, the concomitant use of a stylet and guide wire may be employed for implanting a stimulation lead. Not only is a lead so adaptable, the adaptation may be easily made, requires minimal components, and may be accomplished with tools already made available to the surgeon.
In order to fully appreciate the advance provided by the present invention, it is desirable to review the state of the prior art prior to its conception. Known constructions of leads and their manner of implantation can be found in U.S. Pat. No. 5,489,271 to Andersen, U.S. Pat. No. 5,527,298 to Vance et al. and to U.S. Pat. No. 6,389,320 to Pianca.
Andersen discloses a stylet and hub assembled for stiffening a catheter in rapid exchange mode. The catheter guide wire lumen has a side port associated with a bi-stable guide element that lies across the lumen. A disengageable feature assembly limits insertion of the stylet into the lumen in rapid exchange mode. To convert from rapid exchange mode, disengagement of the disengageable feature enables the stylet to displace the guide element, clearing the guide wire lumen and enabling guide wire or other device to extend throughout the lumen.
Vance et al. disclose a guide wire for placement within a blood vessel for penetrating an occlusion in the vessel. The guide wire comprises a length of flexible wire having a concentric lumen running its entire length. At its proximal end, the wire has an opening to the lumen. At its distal end, the wire has an arcuate tip with a diameter greater than the diameter of the wire immediately proximal thereto. In addition, the guide wire may include a flexible stylet substantially the same length as the guide wire that is removably inserted into the lumen of the guide wire. Such stylet placement provides a greater stiffness and structural integrity to the guide wire. Finally a method of penetrating an occlusion in a blood vessel is disclosed which comprises inserting the guide wire into an occluded blood vessel.
Pianca discloses an implantable stimulation lead readily adaptable for stylet placement or guide wire lead placement. The implantable lead includes at its distal end an implanting guide structure which includes a rigid member having a through bore. A plug is dimensioned to be received within the through bore and a retaining mechanism releasably retains the plug within the through bore. When the plug is retained within the through bore, the lead is adapted for stylet placement and when the plug is released from the through bore, the lead is adapted for guide wire lead placement. In a preferred embodiment, the distal electrode of the lead provides the rigid member of the implanting guide structure. After the lead is positioned by guide wire lead placement, the proximal end of the lead may be sealed with a plug or the plug of the implanting guide structure or new plug may be replaced or placed in the lead to prevent blood flow through the lead.
It was in light of the foregoing known apparatus and techniques that the present invention was conceived and has now been reduced to practice.